SU1737328A1 - Device for determining metal oxidation - Google Patents

Abstract

The invention relates to ferrous metallurgy, in particular to the control of the parameters of a metal in a steelmaking unit, and is intended to determine the oxidation of a metal. The goal is to improve the accuracy of determining the oxidation of the metal. The essence of the invention is that oxidation is determined by means of computer technology, taking into account the temperature of the metal and the environment. The device includes a metal oxidation sensor, a metal temperature sensor and a matching unit. New in the device is that it contains a calibrator, an ambient temperature sensor, a switch, an input sensor switching control unit, a microprocessor control unit and a digital printing unit. 4 ill., 1 tab. sl C

Description

This invention relates to ferrous metallurgy, in particular to the control of the parameters of a metal in a steelmaking unit.

A device for determining

metal oxidation, containing series-connected probe, shrinkage gauge, computing unit and recording instrument. The resulting sample has the shape of a truncated cone with an upper end diameter of 32 mm, and the bottom - 26 mm, sample height 70 mm. Upon receipt of the crystallized sample, an open shrinkage shell is formed, which makes it possible to measure shrinkage without cutting the sample and detecting the cross-section. The shrinkage measurement is carried out by a caliper caliper with an accuracy of 0.1 mm.

The device works as follows.

Non-heated steel is poured into the cup. Immediately after this, the mold is covered with a cardboard cup with an aluminum bar or strip pre-fixed in it in the center of the bottom. After 1.0-1.5 minutes, the cardboard beaker is removed. During this time, the aluminum bar (strip) melts without residue. The sample hardens, it is knocked out of the probe and cooled in water. The caliper of the metal measures the shrinkage of the metal.

In the computing unit, the oxidation of the metal is determined by the following relationship:

,, 06, where 0 - oxidation of the metal,%;

C - metal shrinkage, mm.

VI

s 1

CJ

go

00

When using the known device, there is a low accuracy of controlling the oxidation of the metal in the steel-smelting unit due to the low accuracy of determining the amount of metal shrinkage. In addition, 5 there is a low reproducibility of the results.

The closest in technical essence and the achieved result is a device for determining the oxidation of 10 metal, containing series-connected oxidation sensor. the first amplifier (matching unit), the first functional converter and the first writing unit with a carriage, also containing 15 series-connected metal temperature sensors, the second amplifier (matching unit), the second functional converter and the second writing unit with a carriage, the second output of the second 20 functional converter connected to the second input of the first function converter.

The device works as follows .25

When a temperature sensor is immersed in a liquid metal, thermoEMF appears at its output, proportional to the temperature of the metal, which is amplified and fed to the input of the second functional transmitter, in which the stationary portion corresponding to the metal temperature is determined. A signal proportional to the temperature of the metal enters the second input of the first functional converter and is memorized.

When the oxidation sensor is immersed in the metal, an emf appears at its output, which is amplified by the amplifier and fed to the first input of the first functional converter, in which the oxidation of the metal is determined according to the following relationship:

Ig a0 2,685 10 .087 - E +5661 T +273

where a0 is the oxygen activity in steel,% by mass;

Е - value of emf, mv;

T - metal temperature, ° C.

When using a known device, a low accuracy of control of metal oxidation is observed, due to errors that occur due to the time drift of the gain and the zero shift of the input amplifiers, as well as the effect of the thermopower of the free thermocouple ends on

0 5 0

five

0 5

0

five

0

five

measured signal of metal temperature sensor.

So, for example, when building input amplifiers on operational amplifiers of the KR 140 UD20A type, a change in the ambient temperature by 10 ° C leads to a change in the measured value of oxidation by 10–15% relative to the device readings at the previous ambient temperature (with the same metal oxidation). In the known device, thermoelectric converters are used as the primary metal temperature sensor, which are based on the thermoelectric effect arising in the thermocouple circuit. Calibration tables for standard thermocouples are compiled under the condition that the temperature of the free ends is equal to 0 ° Ј and therefore an amendment must be introduced.

In addition, the known device does not automatically control the moment of switching of input sensors of one-time use, and this leads to the fact that it is possible to falsely determine the oxidation of a metal by random interference occurring in the input measuring circuits in the absence of switching of the input sensors, as well as when the latter .

Thus, a disadvantage of the known device is the low accuracy of control of metal oxidation due to the influence of the thermopower of the free ends of the thermocouple on the value of the measured signal through the channel from the temperature sensor, errors resulting from the time drift of the gain factor and zero offset of the input amplifiers, as well as false determination of the metal oxidation due to random noise occurring in the input circuits of the primary sensors in the event of the latter malfunctioning.

The purpose of the invention is to improve the accuracy of controlling the oxidation of a metal in a steel-smelting unit.

The goal is achieved by the fact that a calibrator, an ambient temperature sensor, a switch, an input sensor switching control unit, a microprocessor control unit, a display unit and a digital control unit are included in the device for detecting metal oxidation, which contains a metal oxidation sensor, a metal temperature sensor and a matching unit. chats, with the outputs of the metal oxidation sensor, a metal temperature sensor, two calibrator outputs, an ambient temperature sensor, and the first output

microprocessor control unit are connected respectively to the first - sixth inputs of the switch, the first output of which is connected to the first input of the microprocessor control unit through the matching unit, to the second input of which the second output of the switch is connected via the switching control unit of the input sensors, the display output is connected to the third input of the microprocessor control unit The second and third outputs of which are connected respectively to the inputs of the display and the digital print unit.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 is a diagram of a calibrator and a switch; in fig. 3 is a diagram of a microprocessor control unit and a digital print unit; figure 4 is a diagram of the display and control unit switching input sensors.

The device (Fig. 1) contains a metal oxidation sensor 1, a metal temperature sensor 2, an ambient temperature sensor 3, a calibrator 4, a switch 5, a matching unit 6, a switching sensor control unit 7 for input sensors, a microprocessor control unit 8, a display 9, a unit 10 digital print

Sensor 1 of metal oxidation can be represented, for example, in the form of a commercially available replaceable unit of the type CB5.189.000. The metal temperature sensor 2 can be represented, for example, in the form of a commercially available thermoelectric converter 11 of the TPR-2p75 type with a range of measured temperatures of 1300-1800 ° C. The ambient temperature sensor 3 can be represented, for example, in the form of a serial thermal converter 12 of the type TCM-6097 with a range of measured temperatures from -50 to 150 ° C. Calibrator 4 is a source of reference voltages and can be performed, for example, on the basis of an operational amplifier 13 of type KR 140UDDA; the resistor 14 sets the current through the zener diode 15, at which the minimum temperature coefficient of voltage is maintained. The Zener diode 15 maintains a voltage of 1 V at the inverse of the operational amplifier 13. The output voltage of the source is equal to

Uon UcT + UR,

where UCT is the stabilization voltage of the zener diode, V;

UR - voltage across the divider resistor, V.

Calibrator 4 can use serial precision resistors as resistors 14 and 16, for example, type C5-60-0.25.

5 The switch 5 can be made, for example, in the form of relay switches 21-25, each of which can be made in the form of a transistor switch 26 and a relay 27 (see FIG. 2).

0 The matching unit 6 (FIG. 3) can be implemented, for example, in the form of an instrumental amplifier having a high input impedance and ensuring the setting of a predetermined gain factor.

5Block 7 sensor switching control

can be performed, for example, in the form of an optical switch 92 and a resistor 93 (see FIG. 4).

Microprocessor control unit 8

0 (FIG. 3) can be performed, for example, in the form of a permanent storage device 28 with a capacity of 2 Kbytes, a register 29. a quartz resonator 30, a single-chip microcomputer 31 of the type KM 1816 BE48, a digital-5 tax converter 32, a register 33, a large integral the serial interface circuit 34. the comparator 35. the source 36 of the reference voltage and the decoder 37.

0 The single-chip microcomputer KM 1816 8Е48 is an LSI that incorporates all the characteristic parts of a small micro computer: an arithmetic-logical device, a control device,

5 reprogrammable ROM of programs with ultraviolet erasure (EPROM), data RAM and software-controlled interface circuits. Dimensions of a single-chip microcomputer 38 KM 1816 BE48: 35,5x5.5x15

0 mm.

The display 9 can be represented, for example, in the form of a large integrated display circuit and keyboard 38, pushbutton switches 39-54, decoder 55

5 of a seven-segment code, a decoder 56. seven-segment indicators 57-72, transistor switches 73-88, transistor 89, resistors 90 and 91, optronic switch 92 and resistor 93 (see Fig. 4).

0 Block 10 digital printing (Fig. 3) can be performed, for example, in the form of a microcontroller 94, transistor buffer 95 and the printing mechanism 96.

The device works as follows.

After turning on the power supply in microprocessor control unit 8, an initialization program starts to be executed, which initializes the device.

In the initial state (see Fig. 2), the transistor switches of the relay switches 21-25 are turned off, and through the normally closed contacts of the relay switch 24 to the thermoelectric converter 2, a probing voltage of 12 V is applied through the current-limiting resistor 93 (see Fig. 4, bl .7). Optocoupler 92 is connected in series to this circuit. If a replaceable thermoelectric converter unit with metal temperature sensor 2 is not installed, then there is no current through optocoupler switch 92, which leads to the formation of a low level signal at its output, which is fed to the input control unit 8 THAT microprocessor 31 and puts the device into the standby mode of installation of the sensor 2 metal temperature. After installing a replaceable thermoelectric converter unit with a metal temperature sensor 2 (see Fig. 4), the + 12V circuit - resistor 93 - optocoupler switch 92 - the temperature sensor 2, metal - (-12V) closes through its low internal resistance, which leads to a high level signal at the output of the optocoupler switch 92 and brings the microprocessor 31 out of the idle state, and the automatic calibration procedure starts in the device.

The automatic calibration procedure is as follows.

The signal from the output of the microprocessor control unit 8 opens the transistor switch 26 (see Fig. 2), which leads to the opening of the normally closed contacts of the relay 27 and connecting the output circuits of the calibrator 4, the output of which is supplied with the voltage Ui (Ui is determined experimentally , proceeding from the output voltage range of the thermoelectric converter of the metal temperature sensor 2), for 8 seconds to the input of the matching unit 6 (the value of A t is determined experimentally), then the transistor switch 26 is closed, which causes The output circuit Ui of the calibrator 4, then the signal from the output of the microprocessor control unit 8 (see Fig. 3) opens the transistor switch of the relay switch 21, which opens its normally closed contacts and connects the output circuits of the calibrator 4 U2 (the U2 value is determined Experimentally, based on the output voltage range of the thermoelectric converter of the metal temperature sensor 2, Ui being selected at the beginning of the range, a DZ

is selected at the end of the output voltage range of the thermoelectric converter of the metal temperature sensor 2) for 8 seconds to the input of the matching unit 6 (the value of A t is determined experimentally), then the transistor switch of the relay switch 21 closes, which causes the calibrator U2 output circuit 4 and connecting the output of the thermoelectric converter of the metal temperature sensor 2 to the output of the matching unit 6.

Next, in the microprocessor control unit 8, the coefficient is calculated

the gain and zero offset magnitude of matching unit 6 according to the following dependencies:

20

k (Ua1 -Ua2) / (Ui-U2),

Uo Ual + Ua2-k (Ul + U2) / 2,

where k is the gain;

Uai is the magnitude of the output voltage of the matching unit when the calibrator first output is connected to its input, V;

Ua2 is the value of the output voltage of the matching unit when connected to its input the second output of the calibrator, V;

Up is the offset value of the zero level of the matching unit at its output, B;

Ui is the voltage value of the first calibrator reference voltage source,

AT; ,,

U2 is the magnitude of the voltage of the second calibrator reference voltage source, V.

Further, the signal from the microprocessor control unit 8 switches the transistor switch of the relay switch 22 and the signal from the thermoelectric converter 11 of the sensor 3 of the ambient temperature is switched to the input

matching block b. The output signal from the matching unit 6, proportional to the ambient temperature, enters the microprocessor control unit 8, where a correction is made to compensate for the thermoEMF of the cold ends of the thermoelectric converter of the metal temperature sensor 2. The real-time calibration procedure lasts no more than 2–3 s, which has almost no effect on

the duration of the full measurement cycle. Moreover, calibration allows eliminating various destabilizing factors (temperature drift, aging of radio elements, etc.), leading to a change in the metrological characteristics of matching unit 6, moreover, during the calibration process, the obtained values of the gain factor k and zero offset Uo are compared with normalized values and in the event of a significant difference caused by the failure of the device’s radio elements, a diagnostic message is generated on the display and the further operation of the device is blocked. Thus, the calibration procedure allows to increase the reliability of the device readings. In the case of normal calibration passing, a readiness message is displayed on the display 9, which is a signal to the beginning of the immersion of the replaceable block of the sensor 2 of the temperature of the metal in the bath of the steelmaking unit. At the same time, the switch 5 is turned on in the switch 5, and through its normally open contacts the thermocouple of the metal temperature sensor 2 is connected to the input of the matching unit 6 and the analog-to-digital conversion program starts to be executed in the microprocessor 31. The ADC code is related to the thermopower value as follows:

  A + Uo,

where Weds is thermoEMF of metal temperature sensor, mV;

k is the gain;

Uo is the zero level offset, mV;

A - ADC code.

The thermopower calculated using the above formula is the initial value for determining the metal temperature in accordance with the nominal statistical characteristic.

The temperature is calculated using the piecewise linear approximation method.

The calculated temperature of the metal T is compared with the lower point of the measured temperature range of 1300 ° C. If T is less, then the above actions are repeated, starting with the ADC, if T is more, the device changes from idle mode to measurement mode, during which the following operations are performed.

The calculated temperature is checked as belonging to the measurable range: 1300 ° C to 1800 ° C.

If T is 1300 ° C and the time t elapsed from the beginning of the measurement is 3 s, then a short measurement message is displayed on the display of the device, the further measurement process

is locked and the device enters the standby mode of installation of the replaceable block of the sensor 2 for measuring the temperature of the metal. The same action is performed if T is 1800 ° C and a message is displayed on the display that the upper limit of the measured range is exceeded. If T belongs to the range of 1300 ° C Ј T Ј 1800 ° C, then its value is recorded in the random access memory and displayed on the display screen.

If T is 1300 ° C and r 3 s, then the measurement process is considered complete and the device proceeds to the processing process of the thermogram recorded in RAM during the measurement. The essence of processing is reduced to a search on the thermogram of a flat area corresponding to the stabilization of the readings of the metal temperature sensor 2. If a shallow area is not found, a poor measurement message is displayed on the device display, if found, the temperature value T in this area, which corresponds to the metal temperature, is displayed on the display screen, in addition, this value is memorized for further use in calculating the metal oxidation.

After that, the device proceeds to wait for a signal from the metal oxidation sensor 1, for which switch 5 changes the state of the relay switches 24 and 25. The relay switch 24 turns off and the relay switch 25 turns on, causing the signal from the metal oxidation sensor 1 to be applied to the input of the matching unit 6,

Before immersion of metal oxidation sensor 1 in liquid metal, the signal from sensor 1 is absent; after immersion in its metal, an emf appears at its output, the value of which is determined in microprocessor control unit 8 according to

  A + Uo,

where E is the EMF value at the output of the metal oxidation sensor when it is immersed in the metal. AT;

k is the gain of the matching unit 6.

Uo zero offset of matching unit 6, V;

A - analog-to-digital converter code.

When the condition E 50mv is fulfilled, the device switches to the EMF measurement mode from the metal oxidation sensor 1, the EMF measurement algorithm is generally similar to

metal temperature measurement algorithm. The difference lies in the measuring range 50mv JЈE: S 800mv and the absence of the piecewise linear approximation procedure, since the measurement of measured values in RAM occurs directly in millivolts. After raising the sensor 1 of the oxidation of a metal from a metal, the EMF disappears at its output and the device proceeds to processing the potentiograms recorded during the measurement in RAM. The result of processing is the average value of the EMF located on a gentle area, corresponding to the stabilization of the readings of the metal oxidation sensor. The measured EMF value E is output to the corresponding line of display 9 and is remembered to directly calculate the oxidation:

(2.685 10 .087 Е + 5661 Т + 273

)

where ao is the oxygen activity in steel,% by mass;

E - the value of the EMF sensor metal oxidation, mv;

T - metal temperature, ° C.

The calculated value of a0 is output to the corresponding line of the display 9 and, in addition, is output via the large integrated circuit of the serial interface 34 of the microprocessor control unit 8 to print the digit printing unit 10. After that, the device returns to its original state.

As tests have shown, the proposed device makes it possible to determine the metal oxidation most closely to its true value.

The table shows the metal oxidation values determined using the prototype device and the proposed device using typical measurements of the metal oxidation in the casting ladle at various ambient temperatures at the working site.

The table shows that the metal oxidation values determined by the prototype device are significantly different from the true values.

RMS values of deviations of the actual oxidation value

metal, determined using the device of the prototype on 212 heats, amounted to 0.0084%, and using the proposed device on the same array of heats - 0.00046%.

Thus, the proposed device makes it possible to determine the value of the oxidation of a metal closest to its true value, and due to a higher accuracy of determining the oxidation of the metal, the consumption of ferromanganese, which sits in the ladle, is reduced.

20

Claims (1)

Invention Formula A device for detecting metal oxidation, comprising a metal oxidation sensor, a metal temperature sensor and a matching unit, characterized by In order to increase the accuracy of metal oxidation determination, a calibrator, an ambient temperature sensor, a switch, an input sensors switching control unit, a microprocessor control unit, a display and a digital printing unit, and two metal oxidation sensor outputs, are entered into it output of the calibrator, ambient temperature sensor, and The first output of the microprocessor control unit is connected respectively to the first - sixth inputs of the switch, the first output of which is connected to the first input of the microprocessor control unit through the matching unit, to the second input of which the second output of the switch is connected through the control block of switching sensors, the display output is connected to the third input of the microprocessor control unit, the second and third outputs of which are connected respectively to the inputs of the display and digital printing unit. Chu fO Fsge .. / Oo, see with g-with gb}   about 1NY g; i about P NJ- “b AND